371 lines
7.7 KiB
Plaintext
371 lines
7.7 KiB
Plaintext
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// SPDX-License-Identifier: GPL-2.0
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// Author: Kirill Smelkov (kirr@nexedi.com)
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//
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// Search for stream-like files that are using nonseekable_open and convert
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// them to stream_open. A stream-like file is a file that does not use ppos in
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// its read and write. Rationale for the conversion is to avoid deadlock in
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// between read and write.
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virtual report
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virtual patch
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virtual explain // explain decisions in the patch (SPFLAGS="-D explain")
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// stream-like reader & writer - ones that do not depend on f_pos.
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@ stream_reader @
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identifier readstream, ppos;
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identifier f, buf, len;
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type loff_t;
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@@
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ssize_t readstream(struct file *f, char *buf, size_t len, loff_t *ppos)
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{
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... when != ppos
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}
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@ stream_writer @
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identifier writestream, ppos;
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identifier f, buf, len;
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type loff_t;
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@@
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ssize_t writestream(struct file *f, const char *buf, size_t len, loff_t *ppos)
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{
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... when != ppos
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}
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// a function that blocks
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@ blocks @
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identifier block_f;
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identifier wait =~ "^wait_.*";
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@@
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block_f(...) {
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... when exists
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wait(...)
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... when exists
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}
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// stream_reader that can block inside.
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//
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// XXX wait_* can be called not directly from current function (e.g. func -> f -> g -> wait())
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// XXX currently reader_blocks supports only direct and 1-level indirect cases.
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@ reader_blocks_direct @
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identifier stream_reader.readstream;
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identifier wait =~ "^wait_.*";
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@@
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readstream(...)
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{
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... when exists
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wait(...)
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... when exists
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}
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@ reader_blocks_1 @
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identifier stream_reader.readstream;
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identifier blocks.block_f;
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@@
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readstream(...)
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{
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... when exists
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block_f(...)
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... when exists
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}
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@ reader_blocks depends on reader_blocks_direct || reader_blocks_1 @
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identifier stream_reader.readstream;
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@@
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readstream(...) {
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...
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}
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// file_operations + whether they have _any_ .read, .write, .llseek ... at all.
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//
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// XXX add support for file_operations xxx[N] = ... (sound/core/pcm_native.c)
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@ fops0 @
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identifier fops;
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@@
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struct file_operations fops = {
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...
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};
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@ has_read @
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identifier fops0.fops;
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identifier read_f;
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@@
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struct file_operations fops = {
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.read = read_f,
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};
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@ has_read_iter @
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identifier fops0.fops;
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identifier read_iter_f;
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@@
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struct file_operations fops = {
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.read_iter = read_iter_f,
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};
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@ has_write @
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identifier fops0.fops;
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identifier write_f;
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@@
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struct file_operations fops = {
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.write = write_f,
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};
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@ has_write_iter @
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identifier fops0.fops;
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identifier write_iter_f;
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@@
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struct file_operations fops = {
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.write_iter = write_iter_f,
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};
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@ has_llseek @
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identifier fops0.fops;
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identifier llseek_f;
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@@
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struct file_operations fops = {
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.llseek = llseek_f,
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};
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@ has_no_llseek @
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identifier fops0.fops;
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@@
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struct file_operations fops = {
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.llseek = no_llseek,
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};
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@ has_noop_llseek @
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identifier fops0.fops;
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@@
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struct file_operations fops = {
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.llseek = noop_llseek,
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};
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@ has_mmap @
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identifier fops0.fops;
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identifier mmap_f;
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@@
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struct file_operations fops = {
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.mmap = mmap_f,
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};
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@ has_copy_file_range @
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identifier fops0.fops;
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identifier copy_file_range_f;
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@@
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struct file_operations fops = {
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.copy_file_range = copy_file_range_f,
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};
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@ has_remap_file_range @
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identifier fops0.fops;
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identifier remap_file_range_f;
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@@
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struct file_operations fops = {
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.remap_file_range = remap_file_range_f,
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};
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@ has_splice_read @
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identifier fops0.fops;
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identifier splice_read_f;
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@@
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struct file_operations fops = {
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.splice_read = splice_read_f,
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};
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@ has_splice_write @
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identifier fops0.fops;
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identifier splice_write_f;
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@@
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struct file_operations fops = {
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.splice_write = splice_write_f,
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};
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// file_operations that is candidate for stream_open conversion - it does not
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// use mmap and other methods that assume @offset access to file.
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//
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// XXX for simplicity require no .{read/write}_iter and no .splice_{read/write} for now.
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// XXX maybe_steam.fops cannot be used in other rules - it gives "bad rule maybe_stream or bad variable fops".
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@ maybe_stream depends on (!has_llseek || has_no_llseek || has_noop_llseek) && !has_mmap && !has_copy_file_range && !has_remap_file_range && !has_read_iter && !has_write_iter && !has_splice_read && !has_splice_write @
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identifier fops0.fops;
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@@
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struct file_operations fops = {
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};
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// ---- conversions ----
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// XXX .open = nonseekable_open -> .open = stream_open
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// XXX .open = func -> openfunc -> nonseekable_open
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// read & write
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//
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// if both are used in the same file_operations together with an opener -
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// under that conditions we can use stream_open instead of nonseekable_open.
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@ fops_rw depends on maybe_stream @
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identifier fops0.fops, openfunc;
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identifier stream_reader.readstream;
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identifier stream_writer.writestream;
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@@
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struct file_operations fops = {
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.open = openfunc,
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.read = readstream,
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.write = writestream,
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};
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@ report_rw depends on report @
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identifier fops_rw.openfunc;
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position p1;
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@@
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openfunc(...) {
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<...
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nonseekable_open@p1
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...>
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}
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@ script:python depends on report && reader_blocks @
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fops << fops0.fops;
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p << report_rw.p1;
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@@
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coccilib.report.print_report(p[0],
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"ERROR: %s: .read() can deadlock .write(); change nonseekable_open -> stream_open to fix." % (fops,))
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@ script:python depends on report && !reader_blocks @
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fops << fops0.fops;
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p << report_rw.p1;
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@@
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coccilib.report.print_report(p[0],
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"WARNING: %s: .read() and .write() have stream semantic; safe to change nonseekable_open -> stream_open." % (fops,))
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@ explain_rw_deadlocked depends on explain && reader_blocks @
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identifier fops_rw.openfunc;
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@@
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openfunc(...) {
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<...
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- nonseekable_open
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+ nonseekable_open /* read & write (was deadlock) */
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...>
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}
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@ explain_rw_nodeadlock depends on explain && !reader_blocks @
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identifier fops_rw.openfunc;
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@@
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openfunc(...) {
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<...
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- nonseekable_open
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+ nonseekable_open /* read & write (no direct deadlock) */
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...>
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}
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@ patch_rw depends on patch @
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identifier fops_rw.openfunc;
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@@
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openfunc(...) {
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<...
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- nonseekable_open
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+ stream_open
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...>
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}
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// read, but not write
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@ fops_r depends on maybe_stream && !has_write @
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identifier fops0.fops, openfunc;
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identifier stream_reader.readstream;
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@@
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struct file_operations fops = {
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.open = openfunc,
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.read = readstream,
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};
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@ report_r depends on report @
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identifier fops_r.openfunc;
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position p1;
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@@
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openfunc(...) {
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<...
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nonseekable_open@p1
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...>
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}
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@ script:python depends on report @
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fops << fops0.fops;
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p << report_r.p1;
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@@
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coccilib.report.print_report(p[0],
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"WARNING: %s: .read() has stream semantic; safe to change nonseekable_open -> stream_open." % (fops,))
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@ explain_r depends on explain @
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identifier fops_r.openfunc;
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@@
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openfunc(...) {
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<...
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- nonseekable_open
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+ nonseekable_open /* read only */
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...>
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}
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@ patch_r depends on patch @
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identifier fops_r.openfunc;
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@@
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openfunc(...) {
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<...
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- nonseekable_open
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+ stream_open
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...>
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}
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// write, but not read
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@ fops_w depends on maybe_stream && !has_read @
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identifier fops0.fops, openfunc;
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identifier stream_writer.writestream;
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@@
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struct file_operations fops = {
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.open = openfunc,
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.write = writestream,
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};
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@ report_w depends on report @
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identifier fops_w.openfunc;
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position p1;
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@@
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openfunc(...) {
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<...
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nonseekable_open@p1
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...>
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}
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@ script:python depends on report @
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fops << fops0.fops;
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p << report_w.p1;
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@@
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coccilib.report.print_report(p[0],
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"WARNING: %s: .write() has stream semantic; safe to change nonseekable_open -> stream_open." % (fops,))
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@ explain_w depends on explain @
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identifier fops_w.openfunc;
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@@
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openfunc(...) {
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<...
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- nonseekable_open
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+ nonseekable_open /* write only */
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...>
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}
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@ patch_w depends on patch @
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identifier fops_w.openfunc;
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@@
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openfunc(...) {
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<...
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- nonseekable_open
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+ stream_open
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...>
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}
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// no read, no write - don't change anything
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